Abstract Lipid compositions and their constituent fatty acids were determined in submerged and aerial leaves, stems, roots, flowers and fruits of Myriophyllum quitense (M. elatinoides Gaudich.) Mono- and digalactosyldiglycerides represented almost half of the total lipids in submerged leaves, while triacylglycerols were the major lipids in fruits and flowers. As regards aerial leaves and stems, neutral lipids constituted the main fraction, although significant amounts of galactolipids were also present. Among phospholipids, phosphatidylethanolamine predominated over phosphatidylcholine in all the tissues, especially stems and roots. Alpha linolenic acid was found to be the main component of glycolipids in submerged and aerial leaves; it was also an important constituent of neutral lipids and phospholipids. In relation to the other tissues, linoleic acid was the predominant acid which was stored in stem and root phospholipids and in fruit and flower neutral lipids. Galactolipids in submerged leaves and stems, triacylglycerols in stems and roots and phosphatidylethanolamine in submerged leaves, stems and roots represented the major lipids showing quantitative changes along the year. The fatty acid unsaturation degree also varied in neutral lipids and phospholipids, being higher in winter. Due to the high content of essential fatty acids and their wide distribution in lipids and tissues, M. quitense may be considered for animal nutrition.